1. Field of the Invention
The invention relates to an integrated control apparatus and an integrated control method for a vehicle having a power train that includes a combination of an internal combustion engine operated at a lean air-fuel ratio that is leaner than a theoretical air-fuel ratio and a stepped automatic transmission.
2. Description of Related Art
Various methods for suppressing generation of a shock that is associated with a gear shift operation of a stepped automatic transmission by cooperative control of the stepped automatic transmission and an internal combustion engine have been suggested. For example, in Japanese Patent Application Publication No. 2009-097445 (JP 2009-097445 A), a method for suppressing the generation of the shock that is associated with the gear shift operation at a time that the stepped automatic transmission is upshifted is disclosed. In the technique of JP 2009-097445 A, torque of the internal combustion engine is temporarily lowered by reducing an intake air amount. In this way, an engine speed is decreased, and the generation of the shock that is associated with the gear shift operation is suppressed. In addition, a method for temporarily lowering the torque by delaying ignition timing is also known.
During upshifting of the stepped automatic transmission, it is preferred to lower the torque of the internal combustion engine at a quick torque response in accordance with switching of engagement of a friction engagement element. However, because there is a delay in response of the intake air amount after an operation of an intake system actuator, such as a throttle, it is difficult to promptly lower the torque only by a reduction in the intake air amount. Meanwhile, the torque can be lowered at a quick torque response by delaying the ignition timing. However, frequent delays in the ignition timing are not preferred because fuel economy of a vehicle is degraded. Furthermore, in a case of the internal combustion engine operated at a lean air-fuel ratio that is leaner than a theoretical air-fuel ratio, the delay in the ignition timing causes unstable combustion. Thus, a magnitude of lowering of the torque that can be achieved by the delay in the ignition timing is limited.